SkyLibrary/build.gradle: tweak the description of the sourcesJar task

SkyLibrary/build.gradle

@@ -53,7 +53,7 @@ javadocJar { archiveBaseName = project.ext.baseName }
 tasks.register('sourcesJar', Jar) {
     archiveBaseName = project.ext.baseName
     archiveClassifier = 'sources'
-    description 'Creates a JAR of sourcecode.'
+    description 'Creates a JAR of Java sourcecode.'
     from sourceSets.main.allJava
 }